How come we're told to eat chicken liver pink? Isn't that a surefire way to get salmonella? Photograph: Rebecca Lovell/guardian.co.uk

We are constantly warned about the dangers of salmonella in chicken, so why does every chef say not to overcook chicken livers and instead serve them pink? How come one is dangerous and the other apparently not?If you overcook chicken livers, they become nasty, bitter, grainy lumps, whereas when pink they have a ­delicate firmness and richness of ­flavour. So can you have salmonella-free livers (and chook) and fabulous flavour? Well, it's all a matter of ­temperature. By that, I mean the ­internal temperature of the livers (or the bird). It's generally ­accepted that to kill off the bacteria quickly you need to get the ­internal temperature to 70C or higher, so provided you get the livers to 70C for a few ­minutes, you should have no problems and it should still be pink in the middle. The same principles apply to roasting a whole bird, so you need a meat thermometer, to check a­ccurately at the ­critical points – the breast next to the bone, where the thighs and legs join and the inside of the thighs. The Food Standards Agency recommends roasting a 2-3kg bird at 190C/375F/gas mark 5 for an hour to an hour and a half, to whack any bugs. However, you'll lose a lot of moisture and thereby flavour by doing so. Can you have the best of both worlds – less loss of f­lavour with a guarantee that your chicken won't poison you? Well, in a column for this very magazine in ­December 2004, Heston ­Blumenthal cited ­research that showed that if you can bring the internal temperature of a turkey to 60C and hold it there for a minimum of 12 minutes, all the stomach-churning bacteria will be no more. And what goes for turkeys goes for chickens – in other words, roast low and slow.

Matthew Fort's roast chicken

Equip yourself with an accurate oven thermometer (most built-in oven controls are in error by between 5% and 15%) and a meat thermometer. Turn your oven on as low as it will go. The oven temperature should be no higher that 100C/gas mark ¼, and preferably lower. The whole point of cooking a bird this way is to bring it as slowly as possible to an internal temperature of 62-65C at all internal points. That way, there will be minimal shrinkage in the fibre structure of the chicken, retaining the maximum juices and flavour inside. Rub the chicken all over with a cut lemon, and place it lying on one side in a roasting pan with a little white wine or water in the bottom. Cook for an hour and a half, then turn over and repeat the dose to the other side for a further hour and a half. Turn the chook on to its breast and roast it breast side down for one and a half hours more. At this point ,it will still feel lukewarm and look raw, but never fear. Use the meat thermometer to test the temperature of the bird at various critical points, namely the breast, the thighs and inside the thighs. They should all be at, or very close to, 62-65C by now. With the bird out of the oven, turn the oven up to its maximum setting and wait for five minutes for it to get really hot. Rub the chicken all over with unsalted butter and sprinkle with salt. Pop it back into the oven the right way up (ie, breast upwards) and roast, basting with the juices from time to time, until browned all over. This should take about 10 minutes. Check the temperatures again. If they're not up to the required 62-65C, leave in for a bit longer. Turn off the oven, leave the chicken to rest for 20 minutes or so, then serve.

I'm quite small and can't eat large amounts, so I find restaurant ­portions far too big. I hardly even dent them, which can be embarrassing, not to mention a waste. Is it bad etiquette to ask for a smaller portion, or for a doggy bag?Strictly speaking, this is a question for an etiquette correspondent, but in their absence I'll do my best. I have every sympathy. I was brought up to finish everything on my plate, and still think it rude if I don't, unless the food is hideous. However, it seems to me that there is no shame in leaving food on the plate in a restaurant. Just ­excuse yourself with a smile to the waiter and by saying something along the lines of, "Please thank the chef for his/her generosity, but it was a little too much for me." You can always ask for a doggy bag, yes, and many restaurants will help you out. In America, in fact, they come as a ­matter of course, though that is probably because the helpings over there are truly Brobdingnagian. To my mind, though, the congealed remains of yesterday's feast never have quite the allure that they did when fresh (though the dog, if you have one, may appreciate the gourmet change of diet).

Every week in winter we get parsnips in our veg box. No matter how I cook them, they have a medicinal aftertaste. Is there a trick to getting that lovely, nutty, sweet taste I know they're capable of delivering?I know the penetrating, slightly ­astringent flavour you mean, and I don't think you're doing anything wrong. Although I wonder if you're cooking the parsnips in an ­aluminium pan – the interaction ­between the acids in the veg and the metal could be producing that medicinal aftertaste. Or possibly they were picked too early. Parsnips like a bit of a cold snap to bring on their true, perfumed flavour and to convert their starch into sugar, a quality greatly appreciated in the sugar-starved ­middle ages. Ask your veg box ­supplier about the ­variety, how they're ­growing them and when they were picked.